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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

268                                  ALASKAN GLACIER STUDIES
for despite the losses by melting and by calving of icebergs, the main cliff was 600 feet farther south on July 6,1910, than on August 24,1909,—314 days earlier.
Pictures from two photographic sites occupied by the Haniman Expedition in June, 1899, and by us in August, 1909, June, 1910, and September, 1910, enable us to check, with graphic proof, the forward movement determined with the transit (Fig. 30). The advance from August, 1909, to June, 1910, was much greater than that of the preceding ten years (Fig. 31). The advance from June, 1910, to September, 1910, which was not measured with the transit, was slight, though perceptible. It may be estimated roughly as over 100 feet.
During the continued advance from June to September, 1910, a large area of dSbris-laden, black ice appeared in the terminal cliff some distance east of the center. It was several hundred yards long and extended 50 or 75 feet above sea level.
The Heather Island Terminus. East of the main ice cliff the Columbia Glacier terminates for about half a mile on an islet north of Heather Island and connected with it at low tide (Fig. 35). The ice front ends successively from west to east (Fig. 32): (1) on a beach (a-c); (2) near a western clump of timber (c-d); (3) on a boggy heath (d-e); (4) near an eastern timber belt (e-h); and (5) on morainic shoals and mud flats in the cove north of Heather Island and east of this islet (h-i). Beyond this is the eastern ice cliff.
This part of the glacier has been visited and studied more than any other and the events in its history for the past ten years are of much interest. In 1899 Gilbertl states that "on the island between the two ice cliffs there were also two push moraines of recent date, the nearer being about 100 feet from the ice front, the farther from 300 to 500 feet. The latter was associated with overthrown forest trees, and included with its rocky debris not only tree trunks and branches but folds of peaty soil. The tract between the nearer push moraine and the ice was in places occupied by an old moraine surface over which the ice had advanced, but this surface was elaborately fluted hi the direction of ice motion, the corrugations having a vertical magnitude of several feet. In one instance it was seen that a large bowlder in the underlying drift had impressed its form, on the ice, preserving in its lee a train of drift of the same cross-section, which constituted a ridge, and it is probable that the other flutings were of the same character. As these details in the configuration of the drift surface would be quickly obliterated by frost and rain, their exposure must have been very recent, Probably the advance creating the push moraine and the subsequent melting which laid bare the ice-molded drift had taken place within one or two years."
Grant visited this same part of Columbia Glacier in 1905, 1908, and June, 1909, and has stated 2 that in 1905 "at the north end of the small island north of Heather Island, on which the front of the glacier is resting, and where a few years ago the glacier had intruded and overturned the front of a forest, a photograph (CVU, A) was obtained from the same position as one (PL CVI, A) taken by Mr. Gilbert in 1899 (Fig. 31, Sta. D). At this point the front of the ice has retreated 160 feet since 1899. On the ground since vacated by the glacier there is very little vegetation—practically nothing except fireweed, which has encroached upon this territory only a few feet."
i Gilbert, 6. K, Harriman Alaska Expedition, Vol. HI, 1904. pp. 77-78.
t Grant, U. S., in H. P. Reid's Variations of Glaciers, Joum. Geol., Vol. XIV, 1906, pp. 406-7; Vol. XVIT, 1909, p. 670.